<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
    </head>
    <body>
        <script>
            let a = 3,
                b = 1;
            a = a + b;
            b = a - b;
            a = a - b;
            console.log(a); // 1
            console.log(b); // 3
        </script>
    </body>
</html>
